The invention concerns the field of devices suitable for controlling the flow of a fluid in a system, and particularly those devices designed to be used in facilities for filling containers.
In container filling machines, it is advantageous to be able to have several flows of fluid, particularly in order to be able to accelerate filling in spite of the foam creation phenomenon. Indeed, when the filling flow is fast, which enables a given volume of product to be filled quickly, the appearance of foam is inevitably observed. This becomes particularly troublesome at the end of filling because the foam causes an overflow of the product, resulting not only in a loss of product, but above all, an ambiguity about the quantity of product that the container actually holds at the end of filling. Obviously, the formation of foam is much less significant if the fill flow is reduced, but this increases the time required for the fill.
It thus appears particularly advantageous to fill the container in two phases. In a first phase, the speed of fill is favored, using a fast flow of fluid without concern for the foaming problem of the product. In a second phase, a slower flow is used to enable any foam that may have been created during the first phase to be reabsorbed and to reach the desired level of fill, either in terms of weight of product, or in terms of volume or height of fill, with the greatest possible precision.
Such a filling procedure requires the use of a means of valve regulation capable of determining at least two different flows of fluid in the system.
One possible solution consists of using a proportional valve that can be controlled to determine a first flow, then a second flow. However, compared to the control electronics of an xe2x80x9call or nothingxe2x80x9d controlled valve, the electronics for a proportional valve are relatively complex and therefore costly. Most filling machines are machines that have a large number of filling stations, each of which must be fitted with its own means of valve regulation. Thus, for machines with several dozen stations-even a hundred stationsxe2x80x94the use of proportional valves is not economically advantageous.
A first object of the invention is therefore to propose a flow control device for fluid, capable of determining two levels of flow. The device must be simple in construction and simple in operation.
To that end, the invention proposes a flow control device for fluid, of the type having valve regulation means that are provided with a threshold through which the fluid circulates, and a movable stop plug that moves inside the chamber between a seated position, in which it rests on the seat to interrupt the passage of fluid through the threshold, and an open position, in which the stop plug is separated from its seat to enable the passage of the fluid through the threshold, characterized in that the device has a second valve regulation means placed in the system in series with the first means of valve regulation, and in which a second movable stop plug moves between a seated position, in which it rests on the seat of a second threshold, and an open position, in which the second stop plug is separated from the second seat to allow the passage of the fluid through the second threshold, and in which, in the seated position, the second stop plug allows the passage of a reduced flow of fluid through the second threshold.
According to other characteristics of the invention:
at least one of the two stop plugs moves between its seated position and its open position under the effect of a magnetic field;
the stop plug moves vertically between its seated position and its open position;
the seated position of the stop plug corresponds to its lower position; it is drawn and held in its upper open position by an electromagnet, and it returns to its seated position under the action of its own weight;
the seated position of the stop plug corresponds to its upper position; it is drawn and held in its lower open position by an electromagnet, and returns and is held in its seated position under the action of a permanent magnet;
the fluid flows in the system in the direction of the movement of the stop plug from its open position to its seated position;
the stop plug is in the shape of a ball and is made from a magnetic material;
the seat of the second means of valve regulation is perforated in such a way as to allow a small section to remain for the fluid to pass through when the stop plug is in the seated position; and
both valve regulation means are built into the same valve body.
The invention also concerns a machine for filling containers, characterized in that it has a device for controlling a flow of fluid that incorporates any one of the preceding characteristics.